Thursday 14 January 2010 07.15 EST
First published on Thursday 14 January 2010 07.15 EST

Yesterday the Welsh Assembly gave the go ahead for a mass cull of thousands of badgers in an attempt to limit the cattle disease bovine tuberculosis (TB) spreading further in Wales. People are welcome to have a personal moral objection to culling badgers, irrespective of their role in transmitting disease. But when objections are based upon the premise that the science linking badgers and TB is somehow ambiguous, then that, in my mind, is tantamount to dismissing Darwin in favour of Noah.

Not that those who think badgers are scapegoats for the farming community can be blamed for holding such a belief. After all, campaigns by groups such as the RSPCA and the Badger Trust have been overwhelmingly successful in distracting public opinion from the less palatable but nevertheless real evidence.

For example, when one-in-eight road-killed badgers were found to be TB positive following a Welsh survey in 2006, the animal rights lobby simply turned logic on its head, proclaiming that "only" one-in-eight Welsh badgers was infected. The rate in cattle at the time was one in 200; some 25 times lower.

Similar spin was placed on an article published in Nature in 2005 that qualified the obvious fact that moving cattle can spread TB. Yet the article did not address the causes of TB in high risk areas, where 85% to 90% of TB incidences actually occur, and an editorial in the same journal clarified that: "To better understand the role of badgers we need to turn to experimental studies, such as the 'Four Counties' trial in Ireland ... By the end of the [Irish] study period the chances of a confirmed TB case in a herd in the [badger] removal areas had fallen by between 62% and 95% relative to the reference areas."

When these were finally published in June 2007 [pdf], they showed mixed results. Removing around 80% of badgers had reduced incidences of TB by almost a quarter during the culling period, but on farms bordering the culling areas incidences had actually increased by a similar amount, due to changes in badger movements (known as "perturbation").

These superficial findings were disappointing to say the least, but closer scrutiny revealed three encouraging trends. First, within the culling areas the risk of TB incidences had fallen, year-on-year, to around a third. Second, in the centre of the proactive culling areas, where badger "perturbation" was not a problem, the number of confirmed incidences had actually halved. And finally, while the number of confirmed incidences on the perimeter of culling areas had actually increased, this effect had reduced over time.

In spite of such mixed findings, the Independent Science Group (ISG) concluded that "badger culling cannot meaningfully contribute to the future control of cattle TB in Britain". Yet from a farming point of view, the data merely identified pitfalls and areas where improvements could be made, and by the time the results were published in a scientific journal a month later, the conclusions had become more ambiguous, with the authors stating that "Careful consideration is needed to determine in what settings systematic repeated culling might be reliably predicted to be beneficial, and in these cases whether the benefits of such culling warrant the costs involved."

But the most significant evidence came in May 2008, with the publication of post-trial data. This showed that the number of confirmed TB incidences in the cull areas had continued to fall after culling stopped, with rates in and around the culling areas 54% and 23% lower than in control areas. By comparison, the number of cattle slaughtered in England and Wales rose by more than 350% between the start of the culling trials and the publication of the post cull results – from 6,000 to more than 27,000. The final count for 2009 is expected to be around 40,000, in spite of a raft of extra cattle controls and new testing regimes having been introduced in the past decade.

So the decision by Welsh rural affairs minister, Elin Jones, to go ahead with a badger cull in a limited area of west Wales is one based firmly upon the science. And given that it will take place in an area with significant geographic boundaries, thus reducing or eliminating "perturbation", and alongside cattle controls that are even stricter than those already in place, the results are likely to be much better than those achieved in the English trials.

In fact, the Welsh approach is the only one that we know will significantly reduce TB incidences; any talk of vaccination, or other approaches, is pure hypothesis. Not only that, but for those who remember the same discussions taking place 20 years ago, vaccination seems like the proverbial end of the rainbow.

So while those who are against culling can base their views on a range of arguments, one that doesn't hold water is that badger culling doesn't work. It does work, and for the 42% of farms in the cull area which have suffered from TB since 2003, the decision of the Welsh Assembly government is long overdue.